An important consideration in the design of radar systems, particularly those for military applications, is the provision of means for recovering radar signals from a total signal which includes noise jamming signals of higher intensity than that of the signal itself. Most noise jammers consist of an oscillator which is frequency modulated by a noisy waveform at high rates. The rates are high enough to shock-excite the victim radar i.f. amplifier so that its output is undistinguishable from true random noise.
Many techniques have been used to attempt elimination of the effects of such jamming signals, for example, side-lobe cancellers and the so-called Dicke Fix.
Side-lobe cancellers reduce interference in antenna side-lobes while not improving any interference in the main lobe. The side-lobe cancellers are also relatively costly since extensive modification must be made to a radar installation including the addition of another antenna and receiver.
The Dicke Fix is used to reduce degradation in the radar display, however, the signal to jam (S/J) ratio is not improved.